<!DOCTYPE html>
<html>
<body>
<canvas id ="canvas" width="200" height="200"></canvas>
<script>
var ctx = document.getElementById('canvas').getContext('2d');
ctx.fillStyle = 'green';
ctx.fillRect(0, 0, 50, 50);
ctx.fillRect(100, 0, 50, 50);
</script>
</body>
</html>